my corolla

i have an 89 corolla, when the weather started getting in the negatives, my car would no longer start... there is a full tank of gas(just in case you wanted to know!) i had the radiotar fluid flushed 2 months ago and the oil changed. the alternator belt needs to be changed and the brake system needs work. i can turn the key and it tries to start, but it wont catch.... my bf's dad cleaned the distributor cap, put gas in the air filter, and heet in the gas tank..... but it still wont start.... im thinking the gas lines are frozen... or something.... i live in montana, would it be best to wait til the weather warms up, get a new battery, or trade my car in?